Great, that is going to drive me crazy trying to figure out how that is done.Hidden mechanism?Optical illusion to hide the camshaft?Stop motion animation?

Nope: all you need to understand is right there. The beams are solidly attached to the big wheel at the center, then run through a circular bearing attached to one of the little wheels at the outside. Engineering genius and reminds me of Michael Moorcock's Chaos symbol in motion.

Found the artist (Brett Dickins) and he has a video of how it's constructed.So, it is a type of camshaft, kind of precarious though, the last arm connected must put a lot of torque on the stepwise circle with the pins.